Glucose transport regulation in most nucleated animal cells is appropriately coordinated with anabolic activity, the transport adjustments usually anticipating recognizable modulations of macromolecular synthesis. Transport is also appropriately responsive to energy need, being stimulated by anoxia, respiratory poisons, fuel deprivation and work. Thymocyte populations consist of cells in two regulatory states as regards glucose transport, active and quiescent, transport in active cells being 20x faster than in quiescent cells. Some agents stimulate quiescent-cell transport 20x in a few seconds, showing that the glucose carrier in quiescent cells is as abundant as in active cells but masked or unavailable. We are attempting to gain insight into the signals mediating masking and unmasking by studying agents and conditions which favor quiescence, which stimulate and which interfere with stimulation by various agents. We will be testing regulatory hypotheses by looking for appropriate effects of presumed signals in thymocyte membrane vesicles and liposomes derived from the vesicles. We will also examine the effects of stimulation in whole cells on properties of the carrier in vesicles and liposomes derived from affected cells.